Inhalers are used to deliver drugs into a patient""s lungs. Typically, an inhaler contains or provides a mixture of drug particles and air or propellant gas. The mixture is delivered via the patient inhaling from a mouthpiece on the inhaler with the air or propellant gas carrying the drug particles into the patient""s lungs.
In dry powder inhalers, the drug particles, in the form of a fine dry powder, are entrained into an airflow, and inhaled by the patient, for treatment for various conditions, for example, bronchial asthma. Drugs delivered via a dry powder inhaler can be used to treat many conditions, including those unrelated to lung conditions, via the systemic absorption of the drug into the bloodstream, via the lung.
For effective dose delivery using a dry powder inhaler, the powder particles must first be dispersed to form a powder/air aerosol. Various techniques for forming powder aerosols have been proposed. Some of these techniques use the airflow from the patient""s inspiration alone to disperse the powder. Other techniques involve forming a powder aerosol by spinning a propeller within a chamber; generating a fast moving flow of air over or through the powder; and shaking, vibrating, or impacting a powder laden string, tape, or mesh, using mechanical devices or ultrasonics. In addition, various other techniques for generating powder aerosols have been proposed or used, with varying degrees of success. Challenges remain in achieving a dry powder inhaler which can effectively create a dry powder aerosol for inhalation, while also having advantages in other areas, such as effectiveness in creating an aerosol, reliability, complexity of design, costs, ergonomics, dose consistency, etc.
Accordingly, it is an object of the invention to provide an improved dry powder inhaler.
To these ends, in a first aspect, a dry powder inhaler has a dispersion chamber. with a central open area surrounded by a bead race. A nosepiece or mouthpiece has at least one outlet opening connecting or entering into the dispersion chamber. One or more inlets also connect into the dispersion chamber. The dispersion chamber contains one or more beads which can move about in the bead race. A powder formulation containing smaller active pharmaceutical particles, and optionally also containing larger inert carrier particles, is placed into or adjacent to the chamber.
When a patient inhales on the mouthpiece, air and powder are drawn into, or flow about within, the dispersion chamber. The beads collide with the interior chamber surfaces, and/or each other, and the powder particles on the chamber surfaces or on the beads. The movement of the beads separate the smaller active drug particles from each other and/or the larger inert carrier particles, if any. In addition to these mechanical forces, other causes of dispersion may include fluid shear between the beads, the powder particles, and the chamber wells. Larger carrier particles, if included in the powder formulation, can further enhance dispersion via enhanced impact energy and abrasion. The active particles are entrained into the airflow through the dispersion chamber, for inhalation by the patient. The larger inert or excipient carrier particles may or may not be entrained and inhaled. The carrier particles are advantageously provided to scour the powder path clean of the fine active particles, so that a more uniform dose may be delivered.
In second and separate aspect of the invention, the beads within the dispersion chamber are induced to move chaotically, so that most or all of the interior surfaces of the dispersion chamber, and the. surfaces of the beads are contacted. As a result, less of the powder may be held up within the dispersion chamber, and a more uniform dose may be delivered. Flow rate performance may also be improved.
In a third and separate aspect of the invention, the flow resistance of a dry powder inhaler is reduced by providing one or more beads into the air flow path of the inhaler. As a result, improved dispersion of powder is achieved, with no additional inspiratory effort by the patient.